1. Field of the Invention
The present invention provides novel antimicrobial immobilized 1,2-benzisothiazolin-3-one/zinc oxide complexes useful as preservatives because of their resistance to being leached from the substrate to which they are attached. This invention also provides substrates having antimicrobial protection including those that require high temperatures in their processing such as, but not restricted to, powder coatings, wood composites and plastics such as polyvinyl chloride (PVC), low-density polyethylene (LDPE), low-density polyethylene foam, plastisols, and polyurethane.
2. Description of the Related Art
Many materials that come into contact with moisture are prone to destructive attacks by a variety of microorganisms including fungi, yeast, algae, and bacteria. Consequently, there is a great need for an effective and economical means to protect such materials from such destructive attacks for extended periods of time. Commercial materials which usually require such protection include, for example, plastics, wood, wood products, wood composites, plastic-wood composites, molded plastics, building materials, paper, toys, coatings, protein-based materials, starch-based compositions, inks, emulsions, resins, stucco, concrete, stone, wood adhesives, caulking, sealants, leather, leather finishes, soap wrappers, packaging materials, spin finishes, fabrics, cordage, carpet backings, electrical insulation, medical devices, and the like.
In addition to protecting commercial materials from such destructive attacks, it is also desirable to inhibit the growth of microorganisms on the surface of the commercial materials to maintain hygienic conditions in, for example, hospitals, nurseries, senior care institutions, food processing facilities, airplanes, trains, buses, and the like.
No single antimicrobial compound provides protection against all microorganisms or is suitable for all applications. In addition to limitations concerning efficacy, other limitations include compound stability, physical properties, toxicological profile, regulatory considerations, economic considerations, and environmental concerns. Antimicrobials that are suitable in many applications may not be suitable in other applications. There is, therefore, a need to develop novel antimicrobial compositions that will provide protection in a variety of applications and under a variety of conditions to protect commercial materials from destructive microorganism attacks and inhibit the growth of microorganisms on the surface of the commercial materials.
A widely used antimicrobial is 1,2-benzisothiazolin-3-one (BIT). BIT and its water-soluble alkali metal salts, are often the biocides of choice when an industrial bactericide is needed to prevent microbial spoilage of water-based technical systems like mineral slurries, polymer emulsions, inks, paints, stucco, adhesives, and the like. (See, for example, W. Paulus “Dictionary of Microbicides for the Protection of Materials” pp. 664-666 (2005), Springer, Dordrecht.)
BIT and its salts are used primarily in liquid systems such as in the coatings industry (paints, varnishes etc.). BIT, and it salts, are used almost exclusively as “in can” preservatives to protect a liquid paint while the paint is in the container before and during application. BIT is not used to protect the coating from microbial growth after it has been applied to the substrate since BIT readily leaches out of the dried coating film.
U.S. Pat. No. 3,065,123 discloses adding 1,2-benzisothiazolin-3-one to an aqueous media to protect the aqueous media from infection by microorganisms. U.S. Pat. No. 4,150,026 discloses metal salt complexes of 3-isothiazolones, which exhibit bactericidal, fungicidal, and algaecidal properties. U.S. Pat. No. 4,188,376 discloses biocidal compositions suitable for indirect food contact applications and in-can preservation of water-based paints comprising a solution of an alkali metal salt of 1,2-benzisothiazolin-3-one in an alcohol, glycol, or water solvent. U.S. Pat. No. 4,871,754 discloses the use of aqueous formulations of the lithium salt of 1,2-benzisothiazolin-3-one to protect aqueous solutions from infestation by microorganisms.
Antimicrobial compounds that are effective as film preservatives, such as Polyphase®, a 3-iodo-2-propynyl butyl carbamate composition, remain in the dried coating and can thereby continue to protect the coating from microbial growth. Polyphase® is mainly effective against fungi and mildew. Accordingly, there is a need for an antibacterial film preservative having the toxicological profile of BIT that will not lose its efficacy over time due to evaporation or leaching. (See W. Lindner in “Chemisch-physikalisches Verhalten von Konservierungsmittel in Beschichtungsstoffen” (1998) Expert Verlag, Bd 509, W. Lindner in “Directory of Microbicides for the Protection of Materials” (2005), W. Paulus (ed) Springer).